In the field of building constructions, it is known to use metal tubular elements of the modular type which are connected to each other to make a tube that allows to transfer concrete from a container, for example a truck-mounted mixer, to a casting zone, by means of pumping devices.
The tube normally comprises rectilinear tubular segments or elements disposed in sequence, which are connected by curved tubular joints, or connector elements, which have standardized angles of longitudinal development, for example 15°, 30°, 45°, 60° or 90°.
The curved tubular elements, compared to the rectilinear ones, are more subject to an abrasive action on the internal surfaces, mainly due to the action of the centrifugal force that the concrete exerts on the internal surfaces, in particular on the part that is external during use, that is, along the extrados.
In particular, along the extrados of the curved tubular joint, the speed of travel of the concrete and its force of impact are much higher than those along the intrados, that is, the zone with the smaller radius of curvature. This leads to a greater wear on the internal surface of the extrados.
A curved tubular joint is known, from the European patent application EP-A-1873440, which comprises a first tubular part, more external, made of material with high mechanical resistance, and a second tubular part, disposed inside the first and made of material with high resistance to wear. In other words, the curved tubular joint consists of two curved tubes, of different material, one inside the other, in which the internal one constitutes an anti-wear lining to increase the working life of the tube.
In this document, to clamp the two tubular parts together, on the external surface of the internal tubular element, near its extrados, spacer elements are made that keep it separate from the external tubular element, in this way to create an interspace which fills with concrete during the first use of the tube: once the concrete has set, it makes the external tubular element solid with the internal one. The known curved joint has the disadvantage, however, that it is rather complex to make, and it is very heavy and very expensive.
This production method has the disadvantage that if the spaces between the two parts are not filled, or not completely filled, this can cause breakages of the internal element, which is produced with very hard materials, resistant to wear, but also very fragile.
On the other hand, it is known that it is very difficult to introduce a curved tubular element inside another curved tubular element because it is necessary to force the parts during the coupling step.
To reduce this complexity, in some known solutions, it is provided to make the internal tubular element in sectors with a circumferential extension, which are inserted individually in the external tubular element and brought close to each other.
However, this known solution does not eliminate these disadvantages completely, and makes the production of the joint complex; it also necessitates another step of clamping the individual components of the second tubular part with respect to the first.
A method to make a curved tubular joint is also known, described in WO2012/017286, which comprises using a curved anti-wear insert which is disposed during use inside the curved tubular element and through which the abrasive material to be transferred passes.
During the production of the curved tubular joint, the curved anti-wear insert is disposed inside a mold and molten steel is cast around its peripheral surface to make an external jacket that, once solidified, forms the external part of the tubular joint. However, this method too is complex and requires long execution times.
One purpose of the present invention is to make a tube for transporting concrete or other abrasive materials in the fluid state which is reliable and long-lasting, simple to make, and relatively light and economical.
Another purpose of the present invention is to make a tube for transporting concrete or other abrasive materials in the fluid state which allows to achieve long operating lives and is also resistant to strong stresses.
Another purpose of the present invention is to perfect an apparatus and a corresponding method to make a tube, or segment of it, having at least one curved segment, which are relatively simple and rapid in execution times.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.